Glass fiber cable, method of making, and its use in the manufacture of track vehicles

ABSTRACT

A coreless glass fiber cable is made of a plurality of individual substantially untwisted glass fiber rovings twisted together. Prior to twisting but during the twisting operation certain of the rovings are impregnated with one component of an elastomeric resin with the remainder of the rovings impregnated with the second component of the elastomeric resin. The impregnated rovings are spirally twisted together in the same direction at substantially the same helical angle, the two components of the elastomeric resin impregnating the rovings mixing with each other at the junction of the intertwining of the rovings to form a cured elastomer spacing the glass fiber rovings and filaments making up the rovings from each other. The layed up glass fiber cable is fed back on itself and subsequent layers of impregnated rovings plied together over the initial layers. The subsequently applied layers are applied at the same helical angle as the initial layer. The cable, although useful for other purposes, is particularly useful in the manufacture of endless track for track vehicles, the endless track comprising a plurality of individual track sections strung along a cable of the type mentioned.

Unite States Patent n 1 Snellman et al.

Feb. 20, 1973 [54] GLASS FIBER CABLE, METHOD OF MAKING, AND ITS USE INTHE MANUFACTURE OF TRACK VEHICLES [75] Inventors: Donald L. Snellman;Willard G.

Hudson, both of Seattle, Wash.

[73] Assignee: Nor-fin, Inc., Seattle, Wash.

[22] Filed: March 31, 1972 [21] Appl. No.: 239,926

Related U.S. Application Data [62] Division of Ser. No. 718, Jan. 5,1970, Pat. No.

[52] U.S. Cl ..305/40 [51] Int. Cl. 55/24 [58] FieldofSearch ..305/35EB,40;57/140 G,

[56] References Cited UNITED STATES PATENTS 3,063,758 ll/1962 Fikse..305/40 3,062,533 5/1972 Shellman....

3,029,590 4/1962 Caroselli....

2,770,940 11/1956 Morrison...

3,029,589 4/1962 Caroselli 3,371,476 3/1968 Costello ..57/149 PrimaryExaminerRichard J. Johnson Attorney-Richard W. Seed et al.

[ 57] ABSTRACT A coreless glass fiber cable is made of a plurality ofindividual substantially untwisted glass fiber rovings twisted together.Prior to twisting but during the twisting operation certain of therovings are impregnated with one component of an elastomeric resin withthe remainder of the rovings impregnated with the second component ofthe elastomeric resin. The impregnated rovings are spirally twistedtogether in the same direction at substantially the same helical angle,the two components of the elastomeric resin impregnating the rovingsmixing with each other at the junction of the intertwining of therovings to form a cured elastomer spacing the glass fiber rovings andfilaments making up the rovings from each other. The layed up glassfiber cable is fed back on itself and subsequent layers of impregnatedrovings plied together over the initial layers. The subsequently appliedlayers are applied at the same helical angle as the initial layer. Thecable, although useful for other purposes, is particularly useful in themanufacture of endless track for track vehicles, the endless trackcomprising a plurality of individual track sections strung along a cableof the type mentioned.

3 Claims, 8 Drawing Figures PATENTED FEB20975 SHEET 2 BF 3 GLASS FIBERCABLE, METHOD OF MAKING, AND ITS USE IN THE MANUFACTURE OF TRACKVEHICLES This is a division of application, Ser. No. 718 filed Jan. 5,1970, now U.S. Pat. No. 3,662,533.

BACKGROUND OF THE INVENTION 1 Field of the Invention This inventionrelates to a coreless multi-strand cable of glass fiber, to a method ofmaking the same, and to an endless track for a track vehicle employingthe cable.

2. Prior Art Relating to the Disclosure Glass fiber cable made up of agroup of glass fiber strands coated with a resinous material is known.For example, see U.S. Pat. Nos. 3,029,590 and 3,371,476. In U.S. Pat.No. 3,029,950 there is disclosed a composite strand structure made up ofbundles of glass filaments embedded in a matrix of elastomeric materialtwisted and plied with similar composite structures to form a yarn whichis then plied with other such structures to form cords or ropes. In U.S.Pat. No. 3,371,476 there is described a glass fiber rope made up ofuntwisted strands which are coated with a lubricant and a thermosettingresin, the coated strands twisted about a core to form a rope. As isnoted in U.S. Pat. No. 3,371,476 cables are usually made using a startercore to control the length of the finished cable and to serve as ananchor for plying initial strands. When such cables are employed forheavy duty work failure of the core of the cable usually occurs prior tofailure of the outer strands making up the cable. One of the primecauses of this failure is believed to be a result of failure of the coreunder tension, failure then progressing to the outer layers.

Endless cables of plied together steel strands have been used to stringa plurality of individual track sections together to form an endlesstrack for track vehicles as described in U.S. Pat. No. 3,063,758.Conventional cables have been found to fail relatively quickly under thesevere operating conditions as a result of internal strand abrasion,outer strand abrasion and fracture of the strands from the effects ofextension bending and flexing. Conventional cables also elongate underthe tension applied when the endless cable is trained about the driveand idler sprockets of a track vehicle. The elongation is such that,after a short period of operation, the endless track not be held inposition about the drive and idler sprockets.

SUMMARY OF THE INVENTION This invention relates to a coreless,substantially homogenous glass fiber cable, to a method of making thesame, and to its use as a linkage for strung together individual trackelements of an endless track vehicle. The cable is made of a pluralityof individual, relatively untwisted glass fiber rovings twistedtogether,.each of the rovings, prior to being twisted together, beingimpregnated with an uncured elastomeric material. Each roving is made upof a plurality of individual filaments. The expressions roving, filamentand cable are defined for purposes of this invention as follows:

roving a plurality of substantially untwisted individual filaments.

filament a fiber of indefinite length.

cable an assembly of twisted together rovings.

The individual rovings are spirally twisted together in the samedirection under substantially the same tension and at substantially thesame helical pitch to produce the cable. The initially spirally twistedrovings are brought back through the junction point of the intertwiningrovings where concentric layers of rovings are twisted thereon under thesame tension and at the same helical angle. The process is continueduntil a cable of the diameter desired is made. Preferably, certain ofthe rovings making up the cable are impregnated with one component of anuncured elastomeric material and the remainder of the rovingsimpregnated with a curing agent or hardener for the uncured elastomer.When impregnated rovings are twisted together the two components areintimately associated resulting in a cured elastomeric material spacingthe individual filaments making up the rovings and the cable from eachother.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view of the apparatusfor making the cable of this invention;

FIG. 2 is a partial perspective view of the planetary winder andassociated means for impregnating the glass fiber rovings making up thecable;

FIG. 3 is a partial view of a section of glass fiber roving used inlaying up the cable of this invention;

FIG. 4 is a partial perspective view of a cable of this invention madeby use of the apparatus of FIG. 1;

FIG. 5 is a partial perspective view of the cable of this inventionincluding an elastomeric sheath surrounding the completed cable;

FIG. 6 is a partial view of a pair of cables of this invention encasedin a block of elastomeric material of a configuration designed tocooperate with individual track sections of an endless track for a trackvehicle;

FIG. 7 is a side elevational view of an endless track of a trackvehicle, the endless track employing cables of this invention to holdthe individual track sections together; and

FIG. 8 is an exploded view of an individual track section of a trackvehicle employing the cable of this invention to hold the individualtrack sections together.

DETAILED DESCRIPTION OF THE INVENTION The glass fiber cable of thisinvention is of substantially homogeneous cross section, has hightensile strength and low elongation. Certain of the rovings making upthe glass fiber cable are coated with one component of a two componentelastomeric material while the remainder of the rovings making up theglass fiber cable are coated with the second component. When theindividual rovings, consisting of substantially parallel untwistedfilaments, are twisted together, the two components react to form acured elastomeric sheath surrounding each of the filaments.

A suitable apparatus for fabricating the cable of this invention isshown in FIGS. 1 and 2. The apparatus comprises a planetary cablingmachine capable of helically winding individual glass fiber rovingstogether without twisting them. A number of spools of glass fiberrovings are spaced around the periphery of the planetary cablingmachine. Adjacent to each of the spools are applicators for applying theuncured prepolymer urethane resin and the polymerizing or curing agentto the rovings. The rovings pass through the applicators. Alternaterovings are impregnated with either uncured resin or curing agent asthey are withdrawn from the spools. A portion of the applicators containuncured resin and the remainder contain a curing agent for the resin ina ratio which produces a cured elastomeric matrix having the desirablephysical characteristics when combined at the point of twisting. Thecable formed by intertwining or plying together of the individual glassfiber rovings is fed back through the juncture or common meeting pointof the intertwined rovings and a subsequent layer of rovings pliedaround the initial layer. The process is continued until a cable of thedesired diameter is obtained. Because of the way the cable is formedthere is no core. Each of the subsequently plied layers isconcentrically applied to the already formed cable so that the angle oftwist or helical angle is substantially the same as in the initiallayer. Throughout formation of the cable, tension on the cable ismaintained substantantially constant. The end result is a coreless cablewith all of the filaments making up the cable at substantially the samehelical pitch and coated with a cured elastomeric sheath.

Referring specifically to FIGS. I and 2 reference numeral 1 denotes theplanetary cabling machine. The machine includes a cabling head 2 aroundthe outer periphery of which are attached a predetermined number ofspool holders 3 for holding glass fiber spools 4. Roving 7 drawn fromeach of the spools 4 mounted on the cabling head 2 passes throughassociated containers S mounted on extension arms 6 before being twistedtogether. Containers hold the liquid components of the elastomericmaterial used to coat each of the individual filaments making up theroving and the finished cable. When a two component elastomeric materialis used, for example, the ratio of the number of containers holding theuncured liquid resin to the containers holding the curing agent orhardener for the resin is adjusted, depending on the resin used. For thepreferred urethane resin, 1 container of liquid resin is used percontainer of curing agent with the curing agent containers interspersedbetween every resin container. The roving from each of the spools ispassed into the interior of the container from one end thereof where itis totally immersed in the liquid component. Wiping orifices 8 at theoutfeed end of each of the containers act to remove excess material fromthe rovings as they pass out of the containers. The cabling head 2 isrotated by means of a variable speed motor 9 driving sprocket 10connected to cabling head 2 by means of chain 11 and sprocket 12. Thetwisted together rovings are trained about driven sheave 13, idlersheave 14 and idler sheave l5, and pass through the hollow axis of thecabling head to the point of intertwining of the rovings issuing fromthe spools mounted on the cabling head. Subsequent layers of roving aretwisted around the initial layup by the rotating motion of the cablinghead.

Sheave 13 is driven by a variable speed motor 16 through suitable drivemeans such as chain 17 trained around sprockets l8 and 19. Idler sheave14 is adjustably mounted so that the tension exerted on the cable, as itis being layed up, can be maintained substantially constant. Idlersheave is preferably located so that the already layed up cable leavesthe sheave in the same plane as the axis of the cabling head.

The rotation rate of cabling head 2 and power sheave 12 are variable (1)to permit variation in the rate of plying roving or speed of cableconstruction and (2) to allow for variation of the roving length of onetwist as the cable diameter increases. As cable diameter increases therate of withdrawal of the glass roving must be greater. This isaccomplished by increasing the speed of rotation of drive sheave 13,thereby allowing the helical angle to be maintained constant as cablediameter increases. By the process described a cable having a fairlysmall and constant helical pitch throughout, i.e. from inner layers ofcable to the outer layers is obtained. In addition, laying up the glassfiber cable at a constant helical pitch reduces internal notching orabrasion which occurs when individual filaments cross over underlyingfilaments in a cable layed up at varying helical angles or cable layedwith the direction of strand lay alternating between initial and finalplies. A cable used as the linkage element for an endless track vehicle,which is not substantially homogeneous in cross-section, weakens anddeteriorates when high loads are applied or when the cable is subjectedto extensive flexing because of internal abrasion or cutting effects ofthe glass fiber filaments. The cable of this invention has no core orstarting cable as distinguished from previous cables used.

A spring tension device 20 is for measuring the tension exerted on thecable being layed up as attached to the shaft of idler sheave 14. Bymaintaining the tension constant on the cable as it is layed up inconjunction with maintaining the helical angle constant, a substantiallyuniform cable is obtained.

FIG. 3 shows a typical glass fiber roving used in the manufacture of thecable of this invention. The glass fiber roving consists of a group ofindividual filaments in substantially parallel untwisted relationship.Glass fiber roving such as that manufactured by Owens Corning Glass Inc.is suitable. The glass fiber filaments usually have a diameter rangingfrom 0.0001 to 0.0006 inches in diameter with the roving comprising to200 filaments.

The elastomeric materials which may be used to individually coat each ofthe filaments making up the rovings are commercially available.Preferably, a two component system is used consisting of a resincomponent and curing agent or hardener for the resin component. Thesecomponents are applied to separate and alternating rovings. When theseparate rovings are twisted together the resin component and the curingagent are intimately associated with each other resulting in cure of theresin. This method of impregnating the individual filaments of the cablewith an elastomeric sheath has distinct advantages over known methods ofapplying resinous material to roving prior to layup of the cable. Manyelastomeric materials, particularly the polyurethanes, have rapid curingtimes. If the components, i.e. the resin and curing agent, are premixedbefore application of the filaments, rapidly increasing viscosity anddegassing are encountered. If too long a time elapses between mixing ofthe components and application to the filaments the elastomeric materialis substantially cured before the filaments are plied together to form acable. By the process described such problems are eliminated. Thissystem allows complete escape of entrained air of the polymer componentswith curing of the polymer delayed by the continuous fresh applicationof the components as each new layer of glass roving is applied over theprevious layer. Excessive tackiness does not develop until after thecable has been completed. The individual filaments making up the cableare each bound to the adjacent filaments by the elastomeric material toform a cable structure having great stability and compactness, the cablestructure not twisting or kinking. Further, because each filament isencased in a sheath of elastomeric material, the inherent fragility ofthe glass fibers, i.e. their low abrasion resistance, is protected. Thisessentially eliminates internal abrasion and fracture as the cable isbent and flexed during usage and particularly during usage as thelinking element for an endless track vehicle.

The amounts of one or both components of the elastomeric materialimpregnating the rovings can be controlled. Elastomeric materials suchas elastomeric polyurethanes and other known elastomeric materials canbe used. Preferably a polyurethane sold under the trade name Uralane isused although similar or identical products are manufactured undervarious trade names.

The finished cable is shown in FIG. 4, the cable comprising a pluralityof individual filaments twisted together at substantially the samehelical angle under constant tension. As can be seen, the cable has nostarter core and is homogeneous in cross section. A cable of any desireddiameter can be fabricated according to the method previously described.For use as the linkage element in endless track vehicles the diameter ofthe cable usually ranges from about seven-eighths to 1 inch or more.

There is an advantage in applying at least one complete external layerof Nylon monofilament to the already layed up cable to prevent abrasionof the glass filaments. Note FIG. 4 wherein a Nylon monofilament 21 ishelically wound around the outer surface of the completed cable. It isalso desirous to encase the complete cable in a sheath of elastomericmaterial 22 as shown in FIG. 5. By doing so internal abrasion of theglass fiber filaments making up the cable is further minimized. Theelastomeric material used may be the same or a different material thanthat used to coat the individual filaments making up the cable.

Although manufacture of the cable has been described using glass fiberroving the cable may be made using other filamentary materials whichhave the physical properties needed.

The cables of this invention are preferably used, as mentioned, as thelinking element in the manufacture of endless track sections for a trackvehicle, such as described in U.S. Pat. No. 3,063,758. FIG. 8 shows apossible configuration of an individual track section. The individualtrack sections are strung on an endless cable of this invention to forman endless track 23 which is trained around idler wheels 24 and powerwheels 25 of a track vehicle 26 as shown in FIG. 7. The cable of thisinvention is encased in a block 20 of elastomeric material having aconfiguration adapted to conform to the configuration needed for holdingin dividual track sections, such as shown in FIG. 8, together. Cablepairs may be embedded within the block of elastomeric material as shownin FIG. 6 or a single cable may be embedded in the passages throughelastomeric blocks 32 shown in FIG. 8. The blocks of elastomericmaterial surrounding the cables of this invention are designed to spaceadjacent track sections and cushion adjacent track sections from eachother to minimize wear and noise.

Generally the track structure, referring to FIG. 8, includes at leasttwo endless cables interconnected by a series of individual tracksections. The track sections are held in registry by means actingbetween adjacent track sections. Elastomeric spacers integral with theelastomeric block in which the cables are encased cushion the individualtrack sections as they move around the driving and idler wheels. Eachindividual track section, (FIG 8) comprises a section body 27 from whichproject lugs 28 while lug receiving cavities 29 are provided in oppositesides of the upper portion of the track sections. The central portionsof the track sections are offset so as to be disposed closely adjacentin adjacent sections. The inner edges of the central portions of thetrack section are formed as curved surfaces to provide a compositestructure to fit into the recess between adjacent teeth of a driving oridler sprocket on the endless track vehicle. On opposite sides of thecentral portions are inwardly projecting bosses 30 which engage the endsof the sprockets to assist in retaining the track on the endless trackvehicle.

The bosses are not located symetrically at opposite ends of the centerof the track section as is evident from FIG. 8 but are offsetsufficiently so that they will lie in adjacent relationship but out ofregistry when the adjacent track sections are assembled. The bosses areof a width considerably greater than the width of the remainder of thetrack section so that the bosses of adjacent track sections will overlapwhen the track sections are assembled in side-by-side relationship.Interengagement of the bosses also functions to limit relative movementof adjacent track sections transversely of the cables in one direction.Each of the track sections includes a cable receiving aperture 31. Asshown in FIG. 8 the access slots communicating with the cable receivingapertures 31 open at opposite ends of the track sections rather thantowards the inner side of such sections. Resilient elements made ofelastomeric material, serving the function of spacer members, are used.These resilient elements may have a configuration such as shown in FIG.8 (ref. no. 32) or in FIG. 6. The block of elastomeric material 32 shownadjacent each track section in FIG. 8 has six spacer projections 33projecting in parallel relationship from one side of the block andspaced apart a distance approximately equal to the thickness of themetal. forming the cable receiving apertures. The cables of thisinvention extend through openings 33a in each of the resilient elements32. On opposite sides of the cable receiving apertures are recesses 34corresponding approximately to the profile shape of the spacerprojections. The spacer projections fit into the recesses when the blockis moved into the cable receiving recesses. When each spacer projectionis received in the recess at the side of the track section end and thetubular portion of the block is fitted in the cable receiving aperture aretainer 35 is inserted behind the elastomer block to hold it in place.The retainer 35 is of generally arcuate shape and includes two fingers36 spaced apart in parallel relationship and adapted to fit into therecesses on opposite sides of the cable receiving aperture so as tostraddle the end portion of the track section in which the apertures areformed. The retainer, once inserted, is struck with a hammer or malletto drive the fingers in until the retainer is in far enough that thenotch 37 of the retainer engages the shoulder 38 in the access slot.When the retainer is in this position the elastomeric material of thespacer members is under sufficient pressure so that the force exerted bythe spacer members against the retainer holds the notch firmly inengagement with the shoulder.

Tests have shown that the cables of this invention have much improvedlife over conventional cables. Internal stresses caused byinter-filament abrasion and breakage occur less frequently. Because ofthe lack of a starter core and the fact that the cable is layed up atsubstantially the same helical pitch and under substantially the sametension, a uniform cable having high tensile strength, low elongationand uniform properties throughout, is obtained. The cable can be made toalmost exact length, i.e. within one-sixty-fourth of an inch bymaintaining the cable under constant tension at all times duringmanufacture thereof.

CABLE STRENGTH AND ELONGATION CHARACTERISTICS A cable was plied asdescribed, to diameter of slightly under one inch. At this dimension thetheoretical breaking strength of the cable is a function of the numberof strands and the individual strength of each strand. The glass strandsused have theoretical breaking strengths which, multiplied by the totalnumber used, yield an endless cable structure having an ultimate tensilestrength of 60 tons. Breaking tests con ducted on cables made accordingto this invention have determined that breakage occurs between 80 and 85percent of the theoretical value, or about 50 tons.

Cables constructed of glass strands according to this invention haveremarkably low elongation characteristics. The theoretical percentelongation of the glass strands used in making the cable wasapproximately 2 percent at the break point. At up to 50 percent of thebreak strength load the percent elongation is less than 1 percent.Elongation of the cable is a function of compaction of strands underincreasing load and the elongation of individual strands. The sum ofthese two factors give an apparent elongation which is determined byload testing up to the break point. Tests performed gave break pointelongations of approximately 2.5 percent. Under loads up to 10 tons theelongation of an endless cable 30 feet in circumferential length andmade according to this invention was less than 2 inches or about 0.6percent. Under an average tractor operating load of 3 tons per cable theelongation would be 1 inch or 0.3 percent.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In a track for an endless track vehicle having cables extendingcircumferentially of the vehicle track and a plurality of individualtrack sections strung on the cable, the cable being a high tension, lowelongation cable, substantially homogeneous in cross-section, made up ofa plurality of substantially untwisted rovings twisted together withoutsubstantial twisting of the individual filaments making up the rovings,each roving comprising a plurality of filaments coated with anelastomenc sheath, the rovmgs being spirally twisted together in thesame direction under constant tension and at the same helical anglewhile the elastomer is in the uncured state.

2. The track of claim 1 including means for each track section forsecuring the cables to the track section.

3. The track of claim 1 wherein said means is a block of elastomericmaterial encasing the cable, the block cushioning and limiting movementof the adjacent track sections.

1. In a track for an endless track vehicle having cables extendingcircumferentially of the vehicle track and a plurality of individualtrack sections strung on the cable, the cable being a high tension, lowelongation cable, substantially homogeneous in cross-section, made up ofa plurality of substantially untwisted rovings twisted together withoutsubstantial twisting of the individual filaments making up the rovings,each roving comprising a plurality of filaments coated with anelastomeric sheath, the rovings being spirally twisted together in thesame direction under constant tension and at the same helical anglewhile the elastomer is in the uncured state.
 2. The track of claim 1including means for each track section for securing the cables to thetrack section.